Process for the production of copolymers containing acrylic acid amides

ABSTRACT

The invention provides a process for the production of ternary and quaternary copolymers containing N,N-disubstituted acrylic acid amides which comprises reacting polyacrylic acid-C1-C4-alkyl ester with secondary alkyl or cycloalkyl monoamines in aprotic solvents at temperatures of from 100* to 250*C and under pressure of from 0 to 100 atms. The reaction products according to the invention are particularly suitable for use as thickeners for printing pastes and as gloss stabilisers for modacrylic filaments and films.

nited States Patent 1.

Korte et al.

PROCESS FOR THE PRODUCTION OF COPOLYMERS CONTAINING ACRYLIC ACID AMIDESllnventors: Siegiried Korte, Leverkusen;

Carlhans Siiling, Odenthal-Hahnenberg; Giinter Lorenz, Dormagen, all ofGermany Assignee: Bayer Aktiengesellschaft,

Leverkusen-Bayerwerk, Germany Filed: Apr. 11, 1973 .Appl. No.: 349,970

Foreign Application Priority Data Apr. Ill, 1972 Germany 2217334 Feb. I,1973 Germany 2304891 US. Cl. 260/795 NV; 260/296 TA;

260/895 S; 260/96 R Int. Cl. C08f 15/40; COSf 27/06; C08f 27/08 Field ofSearch 260/895 S, 80.73, 80.72, 260/79.5 NV, 79.7

[451 July 29,1975

[56] References Cited UNITED STATES PATENTS 2,476,527 7/1949 Barnes260/8 FOREIGN PATENTS OR APPLICATIONS 655,95l l/l938 Germany 1,060,602l/l96l Germany 1,088,231 9/1964 Germany Primary ExaminerStanf0rd M.Levin Attorney, Agent, or Firm-Plumley & Tyner [57] ABSTRACT 4 Claims, 3Drawing Figures FATENTEB JUL 2 9 I975 SHEET FIG. 3

1 PROCESS FOR THE PRODUCTION OF COPOLYMERS CONTAINING ACRYLIC ACIDAMIDES This invention relates to a process for the production of ternaryand quaternary copolymers which contain monomer units ofN,N-disubstituted acrylic acid amides together with acrylic acid andacrylic acid ester groups in the polymer chain.

it is known that copolymers made up of the afore mentioned monomer unitscan be obtained by copollymerising acrylic acid esters, acrylic acid andthe corresponding acrylic acid amides. The structure and composition ofthe products obtained by this process are determined solely by thereactivities of the starting components and by the level of conversionobtained during the polymerisation reaction. Since N,N- disubstitutedacrylic acid amides are only commercially available to a limited extent,production of the aforementioned materials by copolymerisation isgreatly re- :stricted.

The production of special amide-containing copolymers by reactingpolyacrylic acid esters and, corre- :spondingly, polymethacrylic acidesters with ammonia, primary and secondary amides, is described in thePatent literature.

Thus, German Patent Specification No. 655,951 discloses that amines canbe reacted with polyacrylic acid esters in alcoholic or benzenesolution. Under the specified reaction conditions, only relatively lowrates of incorporation of the amine component are obtained with theresult that the process is extremely limited in its scope ofapplication.

it is also known from German Patent Specifications Nos. 1,077,872 and1,088,231 that polymethacrylic acid methyl esters or copolymers largelysynthesised from polymethacrylic acid methyl ester can be reacted withammonia, primary and secondary amines in water as diluent or solvent.Under the described conditions, the use of ammonia and primary aminesresults in the t'ormation of copolymers which, in addition tomethacrylic acid, methacrylic acid amide and methacrylic acid methylester units, also contain as elements of the polymer chain largepercentages of units having a cyclic imide structurev In cases wheresecondary amines are used in the presence of water as diluent orsolvent, the proportion of methacrylic acid which can be attributed tohydrolysis in the polymeric reaction product is extremely high resultingin the formation of copolymers predominantly composed of methacrylicacid units present in the form of their ammonium salts.

in addition, it is known from German Patent Specification No. 1,060,602that particularly reactive secondary amines, such as N-methyl glucamine,can be reacted with polyacrylic acid methyl ester at temperatures of upto 155C in the presence of dimethyl formamide as solvent, thecorresponding acrylic acid methyl ester/acrylic acid amide copolymersbeing formed under the autogenous catalytic effect of the glucamine. Theresulting copolymers are then converted by alkaline hydrolysis in asecond process stage into polymers having acrylic acid units or unitsconsisting of acrylic acid salts. One of the limitations of the processdescribed in German Patent SpecificationNo. 1,060,602 is the fact thatreaction temperatures above 155C are regarded as being unsuitablebecause they promote the formation of crosslinked products.

Accordingly, it was surprising that simple secondary amines should lendthemselves to reaction with polyacrylic acid alkyl esters in aproticsolvents, even in the strict absence of water in the reaction medium, toform ternary or quaternary copolymers which, in addition to the expectedacrylic acid amide and acrylic acid ester units, also contain a largenumber of acrylic acid units in dependence upon the reaction conditions.1t was also surprising that, in contrast to the process described in theabove-mentioned German Patent Specification, secondary amines shouldlend themselves to reaction in aprotic solvents, even at temperaturesvery much higher than 155C, without the polymer being damaged bydegradation or crosslinkingv Accordingly, the present invention providesa process for the production of ternary and quaternary copolymerscontaining N,N-disubstituted acrylic acid amides which comprisesreacting polyacrylic acid-C C,- alkyl esters with amines correspondingto the formula in which R, and R represent identical or differentmembers of the group consisting of C,C,,, alkyl radicals, C -Ccycloalkyl radicals and mixtures thereof, or with amines correspondingto the formula in which n and m represent numbers from 1 to 1 1 whilst Xrepresents a member selected from the group consisting of CH O-, S andN-CH in aprotic solvents at temperatures of from to 250C and underpressures of from 0 to 100 atms.

Polyacrylic acid alkyl esters of the kind obtained in conventionalmanner by the radically initiated polymerisation of acrylic acid alkylesters, represent suitable reagents. Particularly suitable acrylic acidesters include acrylic acid methyl ester, acrylic acid ethyl ester and,optionally, acrylic acid propyl ester and acrylic acid butyl ester.

The following amines are mentioned as preferred reaction components forthe process according to the invention: dimethylamine, methylethylamine,diethylamine, methylpropylamine, methylisopropylamine, ethylpropylamine,ethylisopropylamine, dipropylamine, diisopropylamine, methylbutylamine,ethylbutylamine,

'propylbutylamine, dibutylamine and diisobutylamine.

hexamethylene imine, morpholine, thiomorpholine and N-methylpiperazine.

The reactants, polyacrylic acid alkyl ester and secondary amine, arereacted in the presence of an aprotic solvent in which both the startingcomponents and also the reaction products are readily soluble.

Suitable solvents of this kind include dimethyl formamide,dimethylacetamide, tetramethyl urea, N,N- dimethyl methoxyacetamide,N,N-dimethyl cyanamide, N,N-dimethyl cyanacetamide, hexamethylphosphoric acid triamide, N-methyl pyrrolidone. N-formyl pyrrolidone andN-formyl morpholine.

In order to form ternary copolymers consisting of acrylic acid amide.acrylic acid ester and acrylic acid units, it is advantageous to use theparticular N-formyl or N-acetyl compound on which the secondary amine tobe reacted is based as solvent because the actual polymeranaloguereaction can be preceded by reaction of the secondary amine used withthe solvent. For example, it has been found that, in polymeranaloguereactions carried out in dimethyl formamide with any secondary amines,dimethylamine is liberated to a considerable extent throughtransamidation, participating in the reaction and thus giving rise tothe formation of quaternary copolymers with two structurally differentacrylic acid amide components.

In the polymer-analogue reactions according to the invention, N-methylpyrrolidone acts as a completely inert solvent in which only ternarycopolymers are formed with the acrylic acid amide units derived from thesecondary amine used.

Other aprotic solvents which, basically, perform n dissolving functionon the copolymers to be produced by the process according to theinvention, can be added to a limited extent, more particularly in such aproportion that a homogeneously dissolved system is maintainedthroughout the entire reaction Solvents of this kind are, particularly,aromatic hydrocarbons such as benzene, toluene and xylene. The sole useof an aromatic solvent of this kind can be advisable in special cases,for example in the reaction of long-chain amine components such asmethylstearylamine.

In cases where readily volatile amines and solvents which boil below theintended reaction temperature are used, the polymeranalogue reactionsare carried out in autoclaves designed for pressure of at least up to100 atms. In view of the relatively high reaction temperatures occurringduring the process according to the invention, the following materialswhich are resistant to amine components have proved to be particularlysuitable for the pressure vessels: VAsteel, chromium and titanium.

In many cases, the reaction according to the invention can also becarried out at normal pressure (0 atms.) in non-pressure-tight reactionvessels (for example of glass). This is always possible in cases wherethe boiling temperature of the solvent exceeds the intended reactiontemperature and relatively high boiling amines are used.

The composition of the products obtained by the polymeranalogue reactionis largely determined not only by the type of reactants used and theratio in which they are used, but also by the reaction temperature andthe reaction time. The composition of the copolymer as a function oftemperature after the reaction of polyacrylic acid methyl ester solutionin dimethyl formamide) with 1.4 ml equivalents of dimethylamine for 1hour (FIG. 1) and 10 hours (FIG. 2), is graphically illustrated in FIGS.1 and 2. Curve 1 in FIGS. 1 and 2 corresponds to the N,N-dimethylacrylamide content. Curve 2 in FIGS. 1 and 2 corresponds to theacrylic acid content, whilst curve 3 in FIGS. 1 and 2 corresponds to theacrylic acid methyl ester content. The concentration in percent byweight is shown on the ordinates in FIGS. 1 and 2. The abscissae relateto the temperature as measured in C.

The curves illustrate the reaction sequence characteristic of theprocess according to the invention and the complex reaction mechanism onwhich it is based. Since tertiary amines are formed in an often highconcentration during the reactions, the formation of acrylicacid/ammonium structures in the polymer through the transfer of alkylgroups from the ester to the secondary amine used must be assumed to bethe preliminary stage of the actual amidation process.

The polymer-analogue reaction is carried out at temperatures in therange of from to 250C and preferably at temperatures in the range offrom to 210C.

If allowance is made for the dependence of the copolymer compositionupon the reaction temperature and the molar ratio of the reactioncomponents used, the reaction times can amount to from 1 to 20 hours iffor example an amidation rate of about 80 percent by weight is required.The reaction can be accelerated to a limited extent by the addition ofknown transesterification or amidation catalysts, for example,Namethylate, Na-ethyl, Mg-methylate or lithium hydroxide.

In the process according to the invention, the amine component is usedin a molar ratio of from 0.5 to 2.5, based on the molar content of themonomer units present in the polyacrylic acid alkyl ester. Since, due tothe particular course of the reaction, a large proportion of thesecondary amine component used is converted by alkylation into anonreactive tertiary amine and, for this reason, cannot take part in theactual amidation reaction, a relatively large molar excess of thesecondary amine is always required in cases where it is desired toobtain high amidation rates. The amine component can be added to thereaction mixture all at once at the beginning of the reaction. In manycases, however, it is better to add the amine component eithercontinuously or in portions over a period of time adapted to thereaction time.

The concentration in which the polyacrylic acid alkyl ester solutionsare reacted is governed by the molecular weight of the polyacrylates.For example, from 10 to 25 percent by weight solutions of polyacrylicacid methyl ester in dimethyl formamide or in the other aprotic solventsreferred to above are suitable for the reaction in cases where themolecular weight amounts to between 50,000 and 500,000.

Some of the aforementioned solvents are unstable and decompose under thespecified reaction conditions in the absence of the other components ofthe system. Thus, dimethyl formamide is decomposed to a large extentinto carbon monoxide and dimethylamine at temperatures as low as 180C.It is surprising that, in cases where dimethyl formamide is used, noappreciable decomposition and, hence, no interference with the reactionwere detected in the process according to the invention.

Furthermore, the polymer-analogue reactions. are not accompanied by anydegradation reactions or even crosslinking reactions. becauseprecipitation fractionations show that the molecular weight distributionpredetermined by the polyacrylic acid esters used is maintained.

Since the reaction of polyacrylic acid alkyl esters with secondaryamines in aprotic solvents involves a succession of equilibriumreactions. the amine component added had not been expected to bequantitatively incorporated, especially in reactions carried out inclosed systems. Another factor which has to be taken into considerationis that fairly large proportions of the secondary amine used arealkylated with the result that appreciable quantities of tertiary amineaccumulate in the reaction mixture. In cases where readily volatileamines such as dimethylamine and trimethylamine, for example, are used,the free amines can be separated off fairly easily from the polymersolutions accumulating on completion of the reaction by being distilledoff with an entraining agent, for example with methanol or benzene, in athin-layer evaporator or other apparatus. In the case of less readilyvolatile amines, it is advisable to apply other working-up techniques,for example extraction of the amine components with a solvent which doesnot dissolve the polymeric material or precipitation of the copolymerproduced in the process according to the invention. Residues of freeamine, but above all the amines attached to the polymer in the form oftheir ammonium salts, can readily be separated off by means of an acidion exchanger.

The products according to the invention can be isolated either insolution or in pure form, depending upon the purpose for which theternary or quaternary copolymers containing acrylic acid amides are tobe used. It is advantageous directly to react the polyacrylic acid alkylesters already obtained by solution polymerisation with amines and toleave the reaction products in their dissolved state, even duringworking-up. This applies particularly as regards applications in whichit is desired to subject the solution to shaping operations, as in theproduction of films or fibres.

The invention also provides copolymers obtained by polymeranaloguereaction, consisting essentially of recurring structural unitscorresponding to the formulae (a), (b) and (c):

-CH CH- -CH -CH 2 a 2 D=C-X =C-0H ca 011 -CH in which X 4r: -N\/ 2 CH-CH 2 N-CH3 or the average chemical composition of which is limited bythe concentration ranges of the components of which they are made up,namely to 97 mol of acrylic acid amide (a) 2.5 to mol of acrylic acid(b) 0.5 to 30 mol of acrylic acid methyl ester m with the furthercondition that the molar ratio of acrylic acid to acrylic acid methylester is within the range l:l2 to 110:1.

According to a preferred embodiment, the invention provides copolymersproduced by the process according to the invention, whose averagechemical composition is limited by the concentration ranges .50 to 97mol of acrylic acid amide 2.5 to 35 mol of acrylic acid (h) 0.5 to 15mol of acrylic acid methyl ester (r) with the further condition that themolar ratio of acrylic acid to acrylic acid methyl ester is within therange of from l:6 to I Not all the polymer combinations that areconceivable for a ternary system can be achieved by the process ofpolymer-analogue reaction on account of the special reaction mechanism.If, as is usually the case with ternary copolymers, a triangularcoordinate system is used to describe the chemical composition. thepolymers accumulating during the reaction of polyacrylic acid methylester with secondary amines, especially with dimethylamine, morpholine.thiomorpholine, N-methylpiperazine and methylstearylamine, arerepresented by points situated within the hatched surface of FIG. 3.Coordinate I indicates the N,N-dialkyl acrylic acid amide content,Coordinate II the acrylic acid content and coordinate III theacrylicacid methyl ester content, in each case in mol percent.

We are claiming copolymers having chemical compositions which fallwithin the area 4, 5,76, 7 in FIG: 3. Copolymers of this kind arecommercial interest by virtue of their special properties, above all byvirtue of their solubility in water. 5

Preferred copolymers are those represented in FIG. 3 by the area 4, 8,9, 10 because they are distinguished by their particularly highcompatibility with a number of commercially important polymers.

The reaction products according to the invention are particularlysuitable for use as thickeners for printing pastes, especially thoseproduced by the process described in DOS No. 2,014,763, and as glossstabilisers for modacrylic filaments and films.

Unless otherwise stated, the viscosity numbers [1 quoted in thefollowing Examples were determined in (ill -CH -CH- CHZ-CH (cH -cHdimethyl formamide at 25C.

etc). The acrylic acid content was determined by titration.

Accordingly. addition of the percentage fractions of the componentssynthesising the polymer generally The reaction product which had aviscosity number [nl of 097 formed clear solutions in methanol andwater.

gives values differing from 100 percent.

The following Examples are to further illustrate the EXAMPLES to 9 i vntio wi ho li i i i Following the procedure described in Example 1,

percent polyacrylic acid methyl ester solutions in di- EXAMPLE 1 methyl.fOl'mkLIIllde (molecular weight of the polyme- 240 g of polyacrylicacid methyl ester (molecular 1t) thylacrylatei r= 50.000)- reactedin theO OW- weight M,- 250,000). dissolved in 1.360 g of anhying tests with1.1 mol equivalents of dimethylamine drous dimethyl formamide. werereacted with 140 g of under the conditions set out in the followingTable.

Example 2 3 4 5 6 7 8 9 Reaction conditions: reaction temperature 1C]200 reaction time [hours I 10 l0 l0 l0 l0 l0 10 10 Reaction product:N,N-dimethylacrylamidc content 1% by weight] 3.5 12.7 28.5 53.2 69.369.0 71.8 75.3 acrylic acid content ['71 by weight] 15.3 25.3 39.3 31.524.8 22.1 19.7 18.1 acrylic acid methyl ester content 1% by weight] 82.063.5 30.5 18.1 8.1 8.0 7.9 6.6 viscosity number l-nl 1.01 2.17 1.32 1.161.01 0.94 0.97 0.86

dimethylamine in a 3 litre shaker-type autoclave of tita- EXAMPLES 10 to14 The exce'ss of y fi g g g f l w The tests summarised in the followingTables were 10 percent' tirfidcuon teimpemtur? 9 carried out in a 6litre stirrer-type autoclave of VA- ternal pressure m the reactionvessel inltia 1y rose to -0 steeL The reaction vessel was freed frommoisture by atms" subsequemly fanmg to about 14 the heating andevacuation. Thereafter, 4.000 g batches of gree of Converslon "W {AfterW a Pale an anhydrous 15 percent solution of polyacrylic acid yellowcoloured reaction solution was isolated and a methyl ester in dimethylformamide (molecular weight polymer of the following compositionrecovered from 35 of the po|ymethacrylate fi 240,000) were mm} It: ducedand, after the particular reaction temperature required had beenreached, 440 g of dimethylamine (1.4 mol equivalents) were added over aperiod of 10 40 minutes. The composition of the polymers in dependenceupon the reaction time was determined by samljr ig 'gg g midc plingafter reaction times of l, 2, 3, 4, 6, 8 and 10 acrylic acid methylester 8.5 "/1 h\ \vcight hours.

0 Example Reaction polymer II [5 by time composition: -CH -CH-C-Rweight] Temperature [hours] CH 3 R=N R=0H R=0CH DMF 1. 10.0 5.0 22.272.6

9 Example 332 (.11:.,-01I--R Temperature [hours /CH3 R My), R -OH R 0011J 2 J DMF 1'.6510.0 17.7 50.8 5 08.0"-

mfg 0.0 50.0 I 58.2 29.0

8.0 82.8 10.0 0.5 lZ1 0.09 10.0 85.0 10.1 v 5.9

EXAMPLE 15 pumped into the tightly sealed reaction vessel at 190C thth tt I60 A lOO litre stirrer-type autoclave of VA-steel was W1 6 S mer ummga r p m filled with 60 kg of an anhydrous. l5 solution of 5 polyacrylicacid methyl ester (M 250,000) in di methyl formamide. 9.4 kg i 13.5litres of dimethylamg i '5? 3-3 E zine {2.0 mol equivalents) were thencontinuously umpmg ours N,N-dimethylacrylic acid amide 94.5 by weightacrylic acid 6.55 71 by weight acrylic acid methyl ester 0.55 by weightEXAMPLE 16 1.500 g of a 15 solution of polyacrylic acid butyl ester indimethyl formamide (molecular weight of the polybutylacrylate M.-210,000) were reacted with 1 g of dimethylamine 1.4 mol equivalents) at190C in a 3 litre stirrer-type autoclave of titanium. After 8 30 l 11-ca -c'a-c-x 1% by weight] 12 hours, a terpolymer of the followingcomposition could be recovered from the pale yellow coloured reactionsolution by precipitation with water:

acrylic acid butyl ester 71.4 71 by weight N.N-dimethylacrylamidc 22.0'7: by weight acrylic acid 7.5 7: by weight The isolated copolymer wassoluble in methanol, but insoluble in water.

EXAMPLES 17 to 27 15 solutions of polyacrylic acid methyl ester indimethyl formamide (molecular weight of the polyacrylic acid methylester 171, 250,000) were reacted as in Example 1 with 1.4 molequivalents of the following secondary amines. Copolymers which can becharacterised as follows by their viscosity numbers and theircompositions, could be isolated after reaction at 180C for 8 hours.

amine component polymer composition: viscosity X 4 0311 x -N\R x -Ol-l x-0cn 17) R =R =methyl 85.2 12.7 3.3 -57 1s) R =R =ethyl 64.0 19.7 15.55.5 0.5 19) n =a ro 1 62.4 20.9 12.05 1.2 0.56 20) R =R r -buty1 62.2516.55 15.5 6.1 0.55 21) R =R =is0buty1 56.1 12.7 19.25 11.9 0.50 22) R=ethyl, R =cyc1ohexyl 51.2 22.8 15.7 10.3 0. 48 R =R =cyclohexy1 28.515.7 15.42 12. 0.41.

24) E-Z-N o 62.7 20. 12.4 1.41 0.56

6 A 2 =5 H-a ca 71.2 14.2 11.0 5.6 0.56 27) Q=6 65.7 20.1 12.6 5.6 0.82

. I r r amine component polymer composition: -CH CHC-X 1% by weight]viscosity I M /1 1 H-N 2 x -N\R x -OH x 403 2s) R =R =methy1 72.2 25.16.4 -9 29) R =R =ethy1 71.5 16.1 14.5 -5 R =R =g-propyl 70.8 14.5 45.0-53' 51) R =R =g butyl 65.5 15.1 22.9 52) R =R =isobutyl 48.4 1 5.1- I58.2 I 5 53) R =ethyl R =cyclo- I I i 1 2 hexyl 61.4 18.2 22.5

amine component polymer composition: -CH

by weight] viscosity 1 R lZ i 1 x -N 1 x -oa x -oc: 2 2

5h) R1 =R =cyclohexy1 M .8 16.3 03.5 0.7

Ill-N (CH 157) 7 19.1 3.5 1 .14

581mm o 81.5 17.3 1 .9 0.28

l i 59 H-N s 75.5 18.4 6.9 0.64

hOM-l-N N-CH5 61.2 approximately 25.0 13.7 (L98 EXAMPLES 28 to 40EXAMPLE 41 50 g of polyacrylic acid methyl ester (molecular weight: M,-l30,000), dissolved in 450 g of toluene, were reacted with 82.5 g ofmethylstearylamine (0.5

wherein X is following composition was isolated from the pale yellowcoloured reaction solution following separation of the unreacted aminecomponent:

N-methyl-N-stearyl acrylic acid amide 66.0 by weight acrylic acid methylester 3 I .5 "/1 by weight acrylic acid 3.5 7( by weight We claim:

l. A process for the production of water-soluble copolymers consistingessentially of recurring structural units corresponding to the formulae(a), (h), and (c) mol equivalents) at 180C in a 1.3 litre stirrer-typeautoclave of MA-steel. After 10 hours. a copolymer of the by reactingpolyacrylic acid methyl ester with an amine of the formula in an aproticsolvent consisting essentially of dimethyl formamide. dimethylacetamide.tetramethyl urea. N.N-

A l6 essentially of recurring structural to the formulae (0), (b) and(0) units corresponding dimethyl methoxy-acetamide. N,N-dimethylcyanawhose average chemical composition is determined by mide,N.N-dimethyl cyanacetamide hexamethyl phosphoric acid triamide, N-methylpyrrolidone, N-formyl pyrrolidone or N-formyl morpholine; at atemperature from 160C to 210C under a pressure ofO to 100 atm; for aperiod of time and under conditions to form a copolymer having anaverage chemical composition of:

15 to 97 mol of acrylic acid amide 2.5 to 55 mol of acrylic acid 0.5 tomol of acrylic acid methyl ester the concentration ranges of thecomponents of which they are made up. namely:

15 to 97 mol of acrylic acid amide (a) 2.5 to 55 mol of acrylic acid (h)0.5 to 30 mol of acrylic acid methyl ester (0) with the furthercondition that the molar ratio of acrylic acid to acrylic acid methylester amounts to between 1:12 and 110:1.

4. Water-soluble terpolymers as claimed in claim 3,

30 wherein their average chemical composition 1s limited by theconcentration ranges:

50 to 97 mol of acrylic acid amide (a) 2.5 to 35 mol of acrylic acid (b)0.5 to 15 mol of acrylic acid methyl ester (c) with the furthercondition that the molar ratio of acrylic acid to acrylic acid methylester amounts to between 1:6 and 70:1.

1. A PROCESS FOR THE PRODUCTION OF WATER-SOLUBLE COPOLYMERS CONSISTINGESSENTIALLY OF RECURRING STRUCTURAL UNITS CORRESPONDING TO THE FORMULAE(A), (B), AND (C)
 2. A process as claimed in claim 1, wherein thereaction is carried out in dimethyl formamide, dimethylacetamide orN-methyl pyrrolidone as the aprotic solvent.
 3. Water-solubleterpolymers obtained by the polymer-analogue reaction of polyacrylicacid methyl ester with secondary amines in aprotic solvents, consistingessentially of recurring structural units corresponding to the formulae(a), (b) and (c)
 4. Water-soluble terpolymers as claimed in claim 3,wherein their average chemical composition is limited by theconcentration ranges 50 to 97 mol % of acrylic acid amide (a) 2.5 to 35mol % of acrylic acid (b) 0.5 to 15 mol % of acrylic acid methyl ester(c) with the further condition that the molar ratio of acrylic acid toacrylic acid methyl ester amounts to between 1:6 and 70:1.